Process for the preparation of alkoxytriazolinones

ABSTRACT

Alkoxytriazolinones of the formula (I), ##STR1## in which R 1  and R 2  independently of one another represent in each case optionally substituted alkyl, alkenyl, alkinyl, cycloalkyl, cycloalkylalkyl, aryl or arylalkyl, 
     (which can be used as intermediates for the preparation of herbicidal active compounds) are obtained in good yields and in high purity by reacting iminocarbonic diesters (II) with carbazinic esters (III) ##STR2##  in which R 2  and R 3  in each case represent, for example, alkyl or aryl, 
     at -20° C. to +120° C. (1st step) and subjecting the semicarbazide derivatives (IV) formed in this process with elimination of R 2  -OH ##STR3##  to a cyclizing condensation reaction in the presence of a base at 20° C. to 150° C. with elimination of R 3  --OH, if appropriate (2nd step) and, finally, by reacting the resulting 5-alkoxytriazolinones of the formula (V)  =formula (I) where R 1  =H! with an alkylating agent of the formula R 1  --X (VI)  X, for example,=halogen or --OSO 2  OR 1  ! at 0° C. to 150° C., if appropriate in the presence of a base (3rd step: highly selective 4-alkylation).

This application is a continuation or divisional, of application Ser.No. 08/723,706, filed on Sep. 30, 1996, now U.S. Pat. No. 5,710,303,which is a Divisional of application Ser. No. 08/528,583, filed on Sep.15, 1995, now U.S. Pat. No. 5,599,945.

PROCESS FOR THE PREPARATION OF ALKOXYTRIAZOLINONES

The invention relates to a new process for the preparation ofalkoxytriazolinones, most of which are known and which can be used asintermediates for the preparation of agrochemical active compounds, italso being possible for the process to be carried out on an industrialscale.

Alkoxytriazolinones and a plurality of methods for their preparation arealready known (cf. J. Indian Chem. Soc. 6 (1929), 565-575; J. Chem. Soc.Perkin I 1973, 2644-2646; Arch. Pharm. 307 (1974), 889-891; EP-A 477646;EP-A 507171). However, these known synthetic methods givealkoxytriazolinones only in highly unsatisfactory yields.

It is furthermore known to form5-methoxy-4-methyl-2,4-dihydro-3H-1,2,4-triazol-3-one by methylatingurazole or 4-methylurazole with diazomethane (CH₂ N₂) (cf. F. Arndt etal., Rev. Fac. Sci. Istanbul 13A, pp. 127-144 (1948)); while this methodaffords high yields of the triazolinone, it cannot be carried out on anindustrial scale.

It has now been found that alkoxytriazolinones of the general formula(I) ##STR4## in which R¹ represents in each case optionally substitutedalkyl alkenyl, alkinyl, cycloalkyl, cycloalkylalkyl, aryl or arylalkyland

R² represents in each case optionally substituted alkyl, alkenyl,alkinyl, cycloalkyl, cycloalkylalkyl, aryl or arylalkyl,

are obtained in very good yields and in high purity when iminocarbonicdiesters of the general formula (II) ##STR5## in which R² has theabovementioned meaning

are reacted with carbazinic esters of the general formula (III) ##STR6##in which R³ represents in each case optionally substituted alkyl, arylor arylalkyl,

if appropriate in the presence of a reaction auxiliary and ifappropriate in the presence of a diluent at temperatures between -20° C.and +120° C. ("first reaction step") and the semicarbazide derivativesformed in this process of the general formula (IV) ##STR7## in which R²and R³ have the abovementioned meaning, and/or the correspondingtautomeric compounds are subjected to a cyclizing condensation reaction,at temperatures between 20° C. and 150° C., if appropriate afterintermediate isolation, if appropriate in the presence of a base and ifappropriate in the presence of a diluent ("second reaction step") andfinally reacting the resulting alkoxytriazolinones of the generalformula (V) ##STR8## in which R² has the abovementioned meaning and/orthe corresponding, tautomeric compounds with an alkylating agent of thegeneral formula (VI)

    R.sup.1 --X                                                (VI)

in which

X represents halogen or the groups --O--SO₂ --O--R¹ or --O--CO--O--R¹and

R¹ has the abovementioned meaning, at temperatures between 0° C. and150° C., if appropriate in the presence of a base and if appropriate inthe presence of a diluent ("third reaction step").

Surprisingly, the alkoxytriazolinones of the general formula (I) can beobtained in considerably higher yields by the process according to theinvention than by most of the known synthetic methods. Compared with the"diazomethane method" (F. Arndt et al., 1.c.) the decisive advantage ofthe process according to the invention is that it can also be carriedout on an industrial scale.

What is to be regarded as particularly surprising is the fact that thealkylation of the compound of the formula (V) in the third step proceedswith high selectivity on the N atom in the 4-position and not on any ofthe other N atoms or on the carbonyl oxygen.

In this context, the terms "alkylation" and "alkylating agent" (VI) areused in this context as generic terms and thus expressly include allpossibilities which arise from the above definition of R¹ (i.e. inaddition to R¹ =alkyl, cycloalkyl and arylalkyl, R¹ is also alkenyl,alkynyl, cycloalkyl and aryl).

Since the starting substances required of the formulae (II) and (III)are inexpensive chemicals which are relatively simple to prepare andsince the reactions according to the invention proceed smoothly and inhigh yields, the process according to the invention represents avaluable enrichment of the prior art.

In one possible embodiment of the process according to the invention,all steps can be carried out as a "one-pot reaction", i.e. withoutintermediate isolation of the intermediates.

The invention preferably relates to the preparation of compounds of theformula (I) in which

R¹ represents alkyl, alkenyl or alkinyl, each of which has up to 6carbon atoms and each of which is optionally substituted by cyano,halogen or C₁ -C₄ -alkoxy, or represents cycloalkyl or cycloalkylalkyl,each of which has 3 to 6 carbon atoms in the cycloalkyl moiety and, ifappropriate, 1 to 4 carbon atoms in the alkyl moiety and each of whichis optionally substituted by halogen or C₁ -C₄ -alkyl, or representsaryl or arylalkyl, each of which has 6 or 10 carbon atoms in the arylmoiety and, if appropriate, 1 to 4 carbon atoms in the alkyl moiety andeach of which is optionally substituted by carboxyl, cyano, nitro,halogen, C₁ -C₄ -alkyl, C₁ -C₄ -halogenoalkyl, C₁ -C₄ -alkoxy, C₁ -C₄-halogenoalkoxy or C₁ -C₄ -alkoxy-carbonyl, and

R² represents alkyl, alkenyl or alkinyl, each of which has up to 6carbon atoms and each of which is optionally substituted by halogen orC₁ -C₄ -alkoxy, or represents cycloalkyl or cycloalkylalkyl, each ofwhich has 3 to 6 carbon atoms in the cycloalkyl moiety and, ifappropriate, 1 to 4 carbon atoms in the alkyl moiety and each of whichis optionally substituted by halogen or C₁ -C₄ -alkyl, or representsaryl or arylalkyl, each of which has 6 or 10 carbon atoms in the arylmoiety and, if appropriate, 1 to 4 carbon atoms in the alkyl moiety andeach of which is optionally substituted by carboxyl, cyano, nitro,halogen, C₁ -C₄ -alkyl, C₁ -C₄ -halogenoalkyl, C₁ -C₄ -alkoxy, C₁ -C₄-halogenoalkoxy or C₁ -C₄ -alkoxy-carbonyl.

The invention particularly relates to the preparation of compounds ofthe formula (I) in which

R¹ represents methyl, ethyl, n- or i- propyl or n-, i-, s- or t-butyl,each of which is optionally substituted by cyano, fluorine, chlorineand/or bromine, methoxy or ethoxy, or represents propenyl, butenyl,propinyl or butinyl, each of which is optionally substituted by cyano,fluorine, chlorine and/or bromine, or represents cyclopropyl, cyclobutylor cyclopropylmethyl, each of which is optionally substituted byfluorine, chlorine, bromine, methyl or ethyl, or represents phenyl orbenzyl, each of which is optionally substituted by cyano, fluorine,chlorine, bromine, methyl, ethyl, trifluoromethyl, methoxy, ethoxy,difluoromethoxy, trifluoromethoxy, methoxycarbonyl or ethoxycarbonyl,and

R² represents methyl, ethyl, n- or i- propyl or n-, i-, s- or t-butyl,each of which is optionally substituted by fluorine, chlorine and/orbromine, methoxy or ethoxy, or represents propenyl, butenyl, propinyl orbutinyl, each of which is optionally substituted by cynano, fluorine,chlorine and/or bromine, or represents cyclopropyl or cyclopropylmethyl,each of which is optionally substituted by fluorine, chlorine, methyl orethyl, or represents phenyl or benzyl, each of which is optionallysubstituted by cyano, fluorine, chlorine, bromine, methyl, ethyl,trifluoromethyl, methoxy, ethoxy, difluoromethoxy, trifluoromethoxy,methoxycarbonyl or ethoxycarbonyl.

If, for example, dimethyl imino-carbonate and ethyl carbazinate as wellas methyl bromide are used as starting substances, the course of thereaction in the process according to the invention can be outlined bythe following equation: ##STR9## Formula (II) provides a generaldefinition of the iminocarbonic diesters to be used as startingsubstances in the process according to the invention for the preparationof the compounds of the general formula (I). In formula (II), R²preferably, or in particular, has the meaning which has already beenmentioned above in connection with the description of the compounds ofthe formula (I) preferred or particularly preferred for R².

The starting substances of the formula (II) are known and/or can beprepared by processes known per se (cf. Chem. Ber. 46 (1913), 2447; J.Prakt. Chem. 315 (1973), 640-648; DE-A 1518230; DE-A 4123608).

Formula (III) provides a general definition of the carbazinic estersfurthermore to be used as starting substances in the process accordingto the invention. In formula (III), R³ preferably represents C₁ -C₄-alkyl which is optionally substituted by C₁ -C₄ -alkoxy, or representsphenyl or benzyl, in particular methyl, ethyl, methoxyethyl, ethoxyethylor phenyl.

The starting substances of the formula (III) are known chemicals fororganic synthesis.

The semicarbazide derivatives of the formula (IV) which are formed asintermediates in the first step of the process according to theinvention are new, with the exception of the compounds in which

R² represents phenyl and R¹ represents methyl or tert-butyl;

R² represents 2.2.2-trichloroethyl and R³ represents methyl, ethyl ortert-butyl; and

R² represents 2.2.2-trifluoroethyl and R³ represents methyl, ethyl ortert-butyl.

These eight semicarbazide derivatives, prepared by a different process,have previously been described (cf. G. Zinner, Arch. Pharm. 307, p.889-891 (1974)).

The 5-alkoxytriazolinones of the formula (V) which are formed asintermediates in the second step of the process according to theinvention are also new, with the exception of the compounds in which

R² represents methyl, ethyl, phenyl, 3-methylphenyl, 2,4-dimethylphenylor 3-tert-butylphenyl.

These six alkoxytriazolinones, prepared in each case by other, differentprocesses, have previously been described (cf J. Chem. Soc., PerkinTrans. I, p. 2644-2646 (1973) for R² =CH₃ ; Arch. Pharm. 307, p. 889-891(1974) for R² =C₂ H₅ ; DE-A-19 40 367 for R² =C₆ H₅ and substitutedphenyl as indicated above).

The new semicarbazide derivatives of the formula (IV) and the newalkoxytriazolinones of the formula (V) as such are also a subject of thepresent invention.

Formula (VI) provides a general definition of the alkylating agentsfurthermore to be used as starting substances in the process accordingto the invention. In formulae (VI), R¹ preferably, or in particular, hasthe meaning which has already been mentioned above in connection withthe description of the compounds of the formula (I) as being preferred,or particularly preferred, for R¹.

The starting substances of the formula (VI) are known chemicals fororganic synthesis.

Diluents which are suitable for carrying out the process according tothe invention are (in all reaction steps) the customary organicsolvents. These include, in particular, aliphatic, alicyclic oraromatic, optionally halogenated hydrocarbons such as, for example,benzine, benzene, toluene, xylene, chlorobenzene, dichlorobenzene,petroleum ether, hexane, cyclohexane, dichloromethane, chloroform,tetrachloromethane; ethers such as diethyl ether, diisopropyl ether,dioxane, tetrahydrofuran or ethylene glycol dimethyl ether or ethyleneglycol diethyl ether; ketones such as acetone, butanone or methylisobutyl ketone; nitriles such as acetonitrile, propionitrile orbenzonitrile; amides such as N,N-dimethylformamide,N,N-dimethylacetamide, N-methylformanilide, N-methyl-pyrrolidone orhexamethylphosphoric triamide; esters such as methyl acetate or ethylacetate, sulphoxides such as dimethyl sulphoxide, alcohols such asmethanol, ethanol, n- or i-propanol, n-, i-, s- or t-butanol, ethyleneglycol monomethyl ether, ethylene glycol monoethyl ether, diethyleneglycol monomethyl ether, diethylene glycol monoethyl ether, mixtures ofthese with water, or pure water.

Alcohols such as methanol, ethanol or n- or i-propanol are particularlypreferred as diluents in the first step.

The first step of the process according to the invention is preferablycarried out in the presence of a suitable reaction auxiliary. Suitablereaction auxiliaries are preferably protonic acids such as, for example,hydrochloric acid, sulphuric acid, phosphoric acid, carbonic acid,acetic acid, propionic acid, pivalic acid, methanesulphonic acid,benzoic acid, benzenesulphonic acid and p-toluenesulphonic acid, ifappropriate also polymeric acids or acidic ion exchangers.

Particularly preferred reaction auxiliaries in the first steps of theprocess according to the invention are pivalic acid, acetic acid and(aqueous) hydrochloric acid.

The second and third steps of the process according to the invention arecarried out preferably in the presence of a base. Suitable bases are allthe conventional inorganic or organic bases. These include, for example,the hydrides, hydroxides, amides, alcoholates, acetates, carbonates orhydrogen carbonates of alkaline earth metals or alkali metals such as,for example, sodium hydride, sodium amide, sodium methylate, sodiumethylate, potassium tert-butylate, sodium hydroxide, potassiumhydroxide, ammonium hydroxide, sodium acetate, potassium acetate,calcium acetate, ammonium acetate, sodium carbonate, potassiumcarbonate, potassium hydrogen carbonate, sodium hydrogen carbonate orammonium carbonate, and also basic organic nitrogen compounds such astrimethylamine, triethylamine, tributylamine, N,N-dimethylaniline,N,N-dimethyl-benzylamine, pyridine, N-methylpiperidine,N,N-dimethylaminopyridine, 5-ethyl-2-methyl-pyridine, diazabicyclooctane(DABCO), diazabicyclononene (DBN) or diazabicycloundecene (DBU).

Particularly preferred as bases in the second step of the processaccording to the invention are alkali metal hydroxides, such as sodiumhydroxide or potassium hydroxide, alkali metal alcoholates, such assodium methylate or sodium ethylate, or alkali metal carbonates, such assodium carbonate or potassium carbonate.

When carrying out the first step of the process according to theinvention, the reaction temperatures can be varied within a substantialrange. In general, the process is carried out at temperatures between-20° C. and +120° C., preferably at temperatures between -10° C. and 90°C., in particular at temperatures between 0° C. and 60° C.

When carrying out the second step of the process according to theinvention, the reaction temperatures can be varied within a substantialrange. In general, the process is carried out at temperatures between20° C. and 150° C., preferably at temperatures between 30° C. and 90°C., in particular at temperatures between 40° C. and 80° C.

When carrying out the third step of the process according to theinvention, the reaction temperatures can be varied within a substantialrange. In general, the process is carried out at temperatures between 0°C. and 150° C., preferably at temperatures between 30° C. and 90° C., inparticular at temperatures between 40° C. and 80° C.

All steps of the process according to the invention are generallycarried out under atmospheric pressure. However, it is also possible tocarry out the process under elevated or reduced pressure, in generalbetween 0.1 bar and 10 bar.

For carrying out the process according to the invention for thepreparation of the compounds of the formula (I), 0.5 to 1.2 mol,preferably 0.8 to 1.1 mol, of carbazinic ester of the formula (III) and,1.0 to 3.0 mol, preferably 1.05 to 1.50 mol, of alkylating agent of theformula (VI) are generally employed per mole of iminocarbonic diester ofthe formula (II).

In a preferred embodiment of the process according to the invention, thestarting substances of the formula (II) and of the formula (III) and, ifappropriate, a reaction auxiliary are mixed in a suitable diluent andstirred at the temperature required until virtually no starting materialis present. The intermediate of the formula (IV) can then be isolated inthe customary manner, for example by concentrating the mixture,digesting the residue with an organic solvent, such as, for example,methyl t-butyl ether, and filtering with suction. Alternatively, theintermediate of the formula (IV) can be treated with a base--ifappropriate dissolved in one of the abovementioned diluents--and themixture stirred at the temperature required for cyclizing condensationuntil the reaction has ended, without intermediate isolation. Beforecarrying out the last reaction step, it is preferred not to isolate theintermediate of the formula (V). It can, however, be isolated--ifdesired--for example by concentrating the mixture, taking up the residuein saturated aqueous sodium chloride solution, treating the mixture withan approximately equimolar amount of an acid such as, for example,hydrochloric acid, subjecting the mixture to filtration with suction anddrying the solid product. To alkylate the resulting product, it ispreferably taken up in one of the abovementioned solvents, and themixture is treated with a base and an alkylating agent of the formula(VI) and stirred at the temperature required until the reaction hasended.

Alternatively, the intermediate of the formula (IV) can be reacteddirectly in a one--pot process by alkaline ring closure and, possiblyafter a solvent exchange, with an alkylating agent (VI) to give thealkoxytriazolinone (I), after isolation.

Alternatively, the entire synthetic sequence can also be carried outwithout isolating the intermediates.

Working-up to isolate the products of the formula (I) can be effected bycustomary methods. For example, the mixture is filtered and the filtrateconcentrated, the residue is taken up in an organic solvent such as, forexample, methylene chloride, and the mixture is filtered over silicagel. After the solvent has been removed carefully by distillation underreduced pressure, the product of the formula (I) is then obtained as aresidue.

Alternatively, the reaction mixture can be heated to reflux temperaturein the respective solvent after the alkylation reaction has taken placeand the inorganics can be separated off by hot filtration. By coolingthe filtrate, which is optionally first concentrated more strongly bypartially distilling off the solvent, the products (I) are obtained as aprecipitate, which is filtered off with suction and dried.

The compounds of the formula (I) to be prepared by the process accordingto the invention can be used as intermediates for the preparation ofherbicidally active compounds (cf EP-A 477646 and EP-A 507171).

PREPARATION EXAMPLES Example 1 ##STR10## Steps 1 and 2:

53.6 g (0.5 mol) of ethyl carbazinate are dissolved in 100 ml ofmethanol and, after 1.0 g (0.01 mol) of pivalic acid have been added,213 g of a 23% strength solution of dimethyl iminocarbonate (0.55 mol)in methanol are slowly metered in at 0° C. The mixture is stirred for 2hours at 0° C. and for a further 6 hours at 20° C. 90 g of a 30%strength solution of sodium methanolate (0.5 mol) in methanol are thenadded and the reaction mixture is stirred for 15 hours at 55° C. It issubsequently concentrated, the residue is taken up in 150 ml ofsaturated aqueous sodium chloride solution, and 0.5 mol of concentratedhydrochloric acid are added dropwise at 0° C. After 10 minutes at 0° C.,the mixture is filtered with suction and the solid obtained dried.

38.9 g (68% of theory) of 5-methoxy-2,4-dihydro-3H-1,2,4-triazol-3-oneof melting point 220° C. are obtained (after determining the puresubstance content).

Step 3

10.0 g (87 mmol) of 5-methoxy-2,4-dihydro-3H-1,2,4-triazol-3-one aredissolved in 120 ml of acetonitrile and, after 12.6 g (91 mmol) ofpotassium carbonate have been added, 11.5 g (91 mmol) of dimethylsulphate are added dropwise at 55° C. The reaction mixture is stirredfor 2 hours at 55° C. and then filtered. The filtrate is concentrated,the residue is dissolved in methylene chloride, and the mixture isfiltered over silica gel. The solvent is carefully removed from thefiltrate by distillation under reduced pressure.

The residue is recrystallized from water.

8.4 g (73% of theory--based on the starting material employed in thethird step) of 5-methoxy-4-methyl-2,4-dihydro-3H-1,2,4-triazol-3-one ofmelting point 148° C. are obtained.

Example 2 (Third Step Only) ##STR11##

10.0 g (70 mmol) of 5-propoxy-2,4-dihydro-3H-1,2,4-triazol-3-one (cf.example V-1) are dissolved in 120 ml of acetonitrile and, after 10.1 g(73 mmol) of potassium carbonate have been added, 9.2 g (73 mmol) ofdimethyl sulphate are added dropwise at 55° C. The reaction mixture isstirred for 6 hours at 55° C. and then filtered. The filtrate isconcentrated, the residue dissolved in methylene chloride and thesolution filtered over silica gel. The solvent is carefully removed fromthe filtrate by distillation under reduced pressure.

10.5 g (90% of theory)of4-methyl-5-propoxy-2,4-dihydro-3H-1,2,4-triazol-3-one are obtained asan amorphous product.

Example 3 ##STR12## ("One-pot method")

42.8 g (0.4 mol) of ethyl carbazinate are introduced into 40 ml ofmethanol and, after 128.4 ml of a methanolic solution of 0.44 mol ofdimethyl iminocarbonate have been added, cooled to 0° C. After anaddition of 0.8 ml of concentrated hydrochloric acid (0.008 mol of HCl),the mixture is stirred for 2 hours at 0° C. and then another 24 hours at20° C. 89.5 g of a methanolic solution of sodium methylate (0.42 mol ofNaOCH₃) are subsequently metered in, and the mixture is stirred for 12hours at 55° C. to 60° C. It is then cooled to 20° C., and 37.9 g (0.4mol) of dimethyl sulphate are metered in dropwise. The reaction mixtureis stirred for 2 hours at 40° C., a further 3.8 g (0.04 mol) of dimethylsulphate are added, and stirring is continued for 2 hours at 40° C. Themixture is then concentrated under a water pump vacuum, the residuetaken up in 120 ml of water and the mixture acidified using concentratedhydrochloric acid in an ice-bath. The product obtained as crystals isisolated by filtration with suction.

33.7 g of 5-methoxy-4-methyl-2,4-dihydro-3H-1,2,4-triazol-3-one(content: 90%, yield: 59% of theory over all steps) are obtained.

The following Examples 4 to 6 show how the second and third stage in theone-pot process are carried out: ##STR13##

Example 4: Methylation with Methyl Bromide

50 g (0.306 mol) of ethylN'-(α-amino-α-methoxy-methylene)-hydrazine-N-carboxylate (content:98.5%) are added to a solution of 20.4 g (0.321 mol) of 88% strengthpotassium hydroxide in 220 ml of methanol and the mixture is stirredovernight at 55° C. The methanol is then removed in vacuo, the residueis taken up using 300 ml of propionitrile and cooled to -10° C., 32 g(0.336 mol) of methyl bromide are condensed in and the mixture isstirred at 55° C. under autogenous pressure for 6 hours. The pressurevessel is then let down and the reaction mixture is heated to refluxtemperature and filtered off hot from the insoluble potassium bromide.The filtrate is concentrated to about 100 ml and cooled to -15° C.; theproduct which is deposited during the course of this is filtered off anddried in vacuo.

28.8 g (72% of theory) of5-methoxy-4-methyl-2,4-dihydro-3H-1,2,4-triazol-3-one (content accordingto HPLC against standard: 99%) of melting point 146° C. are obtained.

Example 5: Methylation with Methyl Bromide

70 g (0.428 mol) of ethylN'-(α-amino-α-methoxy-methylene)-hydrazine-N-carboxylate (content:98.5%) are added to a solution of 28.4 g (0.446 mol) of 88% strengthpotassium hydroxide in 300 ml of methanol and the mixture is stirredovernight at 55° C. The solvent is then removed in vacuo, the residue istaken up in 250 ml of methyl isobutyl ketone and cooled to -10° C., 44.4g (0.467 mol) of methyl bromide are condensed in and the mixture isstirred at 55° C. under autogenous pressure for 6 hours.

To determine the yield, after letting down the pressure vessel themixture is evaporated to dryness and the crude product (weight: 103.6 g)is pulverized in a mortar.

Content of 5-methoxy-4-methyl-2,4-dihydro-3H-1,2,4-triazol-3-one againststandard: 47% by weight (corresponds to a yield of 89% of theory);Content of KBr: 45.2% by weight.

Example 6: Methylation with Dimethyl Sulfate

50 g (0.306 mol) of ethylN'-(α-amino-α-methoxy-methylene)hydrazine-N-carboxylate (content: 98.5%)are added to a solution of 20.4 g (0.321 mol) of 88% strength potassiumhydroxide in 250 ml of methanol and the mixture is stirred at 55° C.overnight. It is then concentrated, the residue is taken up in 270 ml ofmethyl isobutyl ketone, and 40.5 g (0.321 mol) of dimethyl sulfate areadded dropwise in the course of 2 hours. After addition is complete, themixture is additionally stirred at 55° C. for a further 2 hours and thenconcentrated to about a third of the original volume and the solids arefiltered off. To remove the inorganics from the filter residue, thesolids are heated to reflux with 200 ml of propionitrile and filteredoff hot. The filtrate is evaporated and the solid residue is dried invacuo.

29.2 g (69.5% of theory) of 5-methoxy-4-methyl-3H-1,2,4-triazol-3-oneare obtained (content: 94%).

Intermediates of the Formula (IV) Example (IV-1) ##STR14## 21.1 g (0.2mol) of ethyl carbazinate are introduced into 20 ml of methanol and,after 61.3 ml of a methanolic solution of dimethyl iminocarbonate with adiester content of 305 g/l (=0.21 mol of diester) have been added, themixture is cooled to 0° C. 0.4 ml of concentrated hydrochloric acid(0.004 mol of HCl) are then added and the mixture is stirred for 6 hoursat 0° C. and for a further 15 hours at 20° C. After a farther 2.9 ml ofthe methanolic solution of dimethyl iminocarbonate have been added, themixture is stirred for a further 6 hours at 20° C. It is thenconcentrated under a water pump vacuum, the residue is stirred with 220ml of t-butyl methyl ether, and the crystalline product is isolated byfiltration with suction.

30.1 g (90% of theory) of ethylN'-(α-amino-α-methoxy-methylene)-hydrazine-N-carboxylate are obtained(content: 96.1%).

¹ H NMR (dimethyl sulphoxide-D₆): 1.165 ppm (3H, triplet); 3.573 ppm(3H, singlet); 3.994 ppm (2H, quartet); 5.887 ppm (2H, singlet); 8.475ppm (1H, singlet).

Example (IV-2) ##STR15## 21.1 g (0.2 mol) of ethyl carbazinate areintroduced into 20 ml of methanol and, after 61.3 ml of a methanolicsolution of dimethyl iminocarbonate with a diester content of 305 g/l(=0.21 mol of diester) have been added, the mixture is cooled to 0° C.0.24 g (0.004 mol) of acetic acid in 2 ml of methanol are then addeddropwise. The mixture is stirred for 6 hours at 0° C. and for a further15 hours at 20° C. It is then concentrated under a water pump vacuum,the residue is stirred with t-butyl methyl ether, and the crystallineproduct isolated by filtration with suction.

30.8 g(93% of theory) of ethylN'-(α-amino-α-methoxy-methylene)-hydrazine-N-carboxylate (content:97.5%) of melting point 134° C. are obtained.

Example (IV-3) ##STR16## 6.0 g (0.041 mol) of dipropyl iminocarbonateand 4.07 g (0.038 mol) of ethyl carbazinate are dissolved in 20 ml ofmethanol, and a solution of 0.19 g (0.0019 mol) of pivalic acid in 2 mlof methanol is added dropwise at 20° C. The mixture is stirred for afurther 15 hours at 20° C. It is then concentrated under a water pumpvacuum, the residue is stirred with 30 ml of t-butyl methyl ether, andthe crystalline product is isolated by filtration with suction.

5.54 g (75% of theory) of ethylN'-(α-amino-α-n-propoxy-methylene)-hydrazine-N-carboxylate (content:96.7%) of melting point 100° C. are obtained.

Example (IV-4) ##STR17## 26.8 g (0.25 mol) of ethyl carbazinate(content: 97%) and 48.4 g (0.30 mol) of di-n-propyl iminocarbonate(content: 90%) are initially introduced into 120 ml of n-propanol atroom temperature, and a solution of 1.53 g (0.015 mol) of pivalic acidin 40 ml of n-propanol is added dropwise in the course of 1.5 hours.After addition is complete, the mixture is additionally stirredovernight and a further 4.8 g (0.03 mol) of dipropyl iminocarbonate and0.5 g of pivalic acid are then added to the reaction mixture. Afterstirring at room temperature for a further 4 hours, the mixture isconcentrated, the residue is treated with 250 ml of petroleum ether andstirred at room temperature for 1.5 hours, and the product is filteredoff.

41.75 g (88.1% of theory) of ethylN'-(α-amino-α-n-propoxymethylene)hydrazine-N-carboxylate (content:98.7%) are obtained.

Intermediates of the Formula (V): Example (V-1) ##STR18## 6.82 g (0.0349mol) of ethyl N'-(α-amino-α-n-propoxy-methylene)-hydrazine-N-carboxylateare dissolved in 40 ml of methanol, and 7.6 g of a solution of 0.0366mol of sodium methylate in methanol is added dropwise at 20° C. Themixture is stirred for 12 hours at 55° C. It is then concentrated undera water pump vacuum, the residue is taken up in 12 ml of water, and thepH is brought to 6 by adding concentrated hydrochloric solution withice-cooling. The product obtained as crystals is isolated by filtrationwith suction.

3.47 g (69.5% of theory) of 5-propoxy-2,4-dihydro-3H-1,2,4-triazol-3-oneof melting point 156° C. are obtained.

Example (V-2) ##STR19## 19.5 g (0.115 mol) of ethylN'-(α-amino-α-methoxy-methylene)-hydrazine-N-carboxylate (content:94.6%) are introduced into a mixture of 20 ml of methanol and 30 ml ofwater and, after 10.8 g of 45% strength aqueous sodium hydroxidesolution have been added (0.12 mol of NaOH), the mixture is stirred for16 hours at 55° C. It is then concentrated under a water pump vacuum,the residue is taken up in 30 ml of water, the mixture is acidifiedusing concentrated hydrochloric acid with ice-cooling, and the productobtained as crystals is isolated by filtration with suction.

10.0 g (76% of theory) of 5-methoxy-2,4-dihydro-3H-1,2,4-triazol-3-oneare obtained.

Example (V-3): Stages 1 and 2 in the One-pot Process ##STR20## 50 g(0.345 mol) of di-n-propyl iminocarbonate (content: 99.2%) and 33.7 g(0.314 mol) of ethyl carbazinate (content: 97%) are initially introducedinto 130 ml of n-propanol, and a solution of 1.6 g (0.0157 mol) ofpivalic acid in 20 ml of n-propanol is added dropwise at roomtemperature in the course of 1.5 hours. After addition is complete, themixture is additionally stirred at room temperature overnight and 73.4 g(0.345 mol of NaOCH₃) of a methanolic solution of sodium methylate arethen added dropwise; the reaction mixture is then additionally stirredat 55° -60° C. for 22 hours. The solvent is subsequently removed invacuo and the residue is treated with 40 ml of ice-water and 160 ml ofn-butyronitrile; this mixture is acidified with cooling by addition ofconcentrated hydrochloric acid and heated to 85° C., then the two phasesare separated. The aqueous phase is treated a further two times(extracted) at 85° C. with 40 ml of n-butyronitrile each time, and thecombined organic phases are washed with 15 ml of saturated sodiumchloride solution and evaporated in vacuo. The residual solid is stirredwith 300 ml of petroleum ether and the product is filtered off.

45.7 g (91.1% of theory, over the two stages, based on ethyl carbazinateemployed) of 5-propoxy-2,4-dihydro-3H-1,2,4-triazol-3-one are obtained(content: 89.5%).

We claim:
 1. Alkoxytriazolinone of the formula (V) ##STR21## in which R²represents n-propyl, i-propyl, propenyl or cyclopropylmethyl. 2.5-(n-Propoxy)-2,4-dihydro-3H-1,2,4-triazol-3-one according to claim 1.